High-frequency circuit package and sensor module

ABSTRACT

Shielding of high-frequency circuits is achieved using a simple and inexpensive configuration not using any lid. A high-frequency circuit mounting substrate ( 20 ) is disposed, on an underside surface layer of which are disposed high-frequency circuits ( 21  and  22 ) and is formed a first grounding conductor that has same electric potential as grounding conductors of the high-frequency circuits and that surrounds the high-frequency circuits. A mother control substrate ( 3 ) is disposed, on which the high-frequency circuit mounting substrate ( 20 ) is mounted in such a way that the high-frequency circuits are sandwiched therebetween and on which a second grounding conductor is formed in a region facing the high-frequency circuits. Plural first lands are formed on the first grounding conductor of the high-frequency circuit mounting substrate ( 20 ) to surround the high-frequency circuits. Plural second lands are formed that are electrically connected to the second grounding conductor at positions on a surface layer of the mother control substrate ( 3 ) which face the first lands. Plural solder balls ( 30 G 2 ) are disposed for connecting the first lands and the second lands. The high-frequency circuits are housed in pseudo shielding cavities surrounded by the solder balls ( 30 G 2 ), the grounding conductors of the high-frequency circuits, and the first and second grounding conductors.

FIELD

The present invention relates to a high-frequency circuit package inwhich a high-frequency circuit mounting substrate having ahigh-frequency circuit mounted thereon and a mother control substratehaving a waveguide formed thereon are BGA-connected with solder balls,and relates to a sensor module.

BACKGROUND

In a high-frequency package, in which high-frequency circuits aremounted that operate in high-frequency bands such as millimeter wavebands, the high-frequency circuits are mounted in a cavity that iselectrically shielded using a seal ring, a lid and the like, takingairtightness for weather resistance, operating stability and the EMI(radioactive spurious) standard into consideration.

In Patent Document 1, a semiconductor chip and a circuit substrate aremounted in an outer case. In order to establish a connection with awaveguide disposed on the downside of the circuit substrate and theouter case, a dielectric window having a stripline antenna formedthereon is disposed immediately above the waveguide. The striplineantenna is connected to the circuit substrate via a stripline so thatthe waveguide disposed below the dielectric window is connected thereto.The upside opening of the outer case is sealed with a lid in an airtightmanner.

CITATION LIST Patent Literature

-   Patent Document 1: Japanese Patent Application Laid-open No.    H05-343904 (FIG. 3)

SUMMARY Technical Problem

In the conventional package structure, the high-frequency circuits areshielded by the lid and the outer case that serves as a seal ring.Hence, as far as the cost and high-volume production is concerned, thereexist a lot of barriers such as an increase in the number of componentsincluding the lid and the seal ring, and an increase in the complexityof the manufacturing process including performing solder joints to thepackage and performing welding of the lid. Thus, there has been a demandfor a simple package structure and a simple module configuration thatwould enable achieving electromagnetic shielding and isolation at a lowcost even for high-frequency bands such as microwave bands or millimeterwave bands.

In recent years, with the advance in the development regarding weatherresistance enhancement of semiconductor chips or high-frequencycircuits, protective films are formed over semiconductor circuits inorder to achieve reliability that is required in a system. That has ledto the implementation of non-airtight packages for, e.g., modules inwhich circuits are mounted directly on a resin substrate.

The present invention has been made in view of the above and an objectthereof is to provide a high-frequency circuit package and a sensormodule that enable achieving shielding of high-frequency circuits orachieving isolation among a plurality of high-frequency circuits using asimple and inexpensive configuration and not using any lid.

Solution to Problem

To solve the problem described above and achieve the object, the presentinvention includes: a first dielectric substrate having a high-frequencycircuit disposed on an underside surface layer and having a firstgrounding conductor that has same electric potential as a groundingconductor of the high-frequency circuit and that is formed on theunderside surface layer to surround the high-frequency circuit; and asecond dielectric substrate, on which the first dielectric substrate ismounted in such a way that the high-frequency circuit is sandwichedtherebetween, the second dielectric substrate having a line formedthereon for supplying a signal to drive the high-frequency circuit andhaving a second grounding conductor formed in a region that faces thehigh-frequency circuit, wherein a plurality of first lands are formed onthe first grounding conductor of the first dielectric substrate tosurround the high-frequency circuit, and a plurality of second lands areelectrically connected to the second grounding conductor and are formedat positions on a surface layer of the second dielectric substrate whichface the plurality of first lands, a plurality of conductive connectingmembers are disposed for connecting between the first lands and thesecond lands, and the high-frequency circuit is housed in a pseudoshielding cavity that is surrounded by the plurality of conductiveconnecting members, the first and second grounding conductors, and thegrounding conductor of the high-frequency circuit.

Advantageous Effects of Invention

According to the present invention, the high-frequency circuit formed onthe underside surface layer of the first dielectric substrate is housedin the pseudo shielding cavity that is surrounded by the conductiveconnecting members formed around the high-frequency circuit, first andsecond grounding conductors, and grounding conductor of thehigh-frequency circuit. Hence, it becomes possible to shield thehigh-frequency circuit using a simple and inexpensive configuration andnot using any lid.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view of a sensor module according to anembodiment of the present invention.

FIG. 2 is a cross-sectional view of a high-frequency circuit packageaccording to the embodiment of the present invention.

FIG. 3 is a plan view of an arrangement example of high-frequencycircuits, high-frequency semiconductor chips, and BGA balls formed on anunderside surface layer of a high-frequency resin substrate in thehigh-frequency circuit package according to the embodiment of thepresent invention.

FIG. 4 is a cross-sectional view of a configuration of awaveguide-microstrip converter portion formed in the high-frequencycircuit package according to the embodiment of the present invention.

FIG. 5 is a perspective view of the configuration of thewaveguide-microstrip converter portion formed in the high-frequencycircuit package according to the embodiment of the present invention.

FIG. 6 is a plan view of another arrangement example of high-frequencycircuits, high-frequency semiconductor chips, and BGA balls formed onthe underside surface layer of a high-frequency resin substrate in thehigh-frequency circuit package according to the embodiment of thepresent invention.

DESCRIPTION OF EMBODIMENTS

An exemplary embodiment for a high-frequency circuit package and asensor module according to the present invention will be described belowin detail with reference to the accompanying drawings. The presentinvention is not limited to the embodiment described below.

FIG. 1 is a diagram illustrating a configuration of a sensor moduleaccording to an embodiment of the present invention. The sensor moduleis applicable to a millimeter-wave radar that transmits and receivesradio waves of millimeter wave bands. On a control antenna substrate 1having a power source for high-frequency circuits mounted thereon andhaving control circuits mounted thereon, a transmitting circuit packageTX and a receiving circuit package RX are also mounted as high-frequencycircuit packages. In the transmitting circuit package TX as well as inthe receiving circuit package RX, a plurality of high-frequency circuitsare mounted that operate in high-frequency bands such as microwave bandsor millimeter wave bands. In the transmitting circuit package TX as wellas in the receiving circuit package RX, the high-frequency circuits arehoused in a non-airtight manner but with adequate humidity resistance.The circulation of water molecules between the inside and the outside ofthe packages is not blocked. Meanwhile, the millimeter-wave radar can bea FW-CW radar, a pulse radar, a multifrequency CW radar, or the like;but the radar method is not limited thereto. The sensor module can alsobe applied to communication devices or to microwave radars.

The control antenna substrate 1 is configured as an integrated structureof a resin antenna substrate 2 having antenna patterns (antennaelements) arranged thereon and a mother control substrate 3 made ofresin and having a transmitting waveguide 4, a receiving waveguide 5(one or more), and a triplet line 6 formed thereon. The control antennasubstrate 1 is configured by bonding a resin substrate having excellenthigh-frequency transmission characteristic and a dielectric substratemade of ceramic or the like. Apart from the transmitting circuit packageTX and the receiving circuit package RX, various non-illustrated controlcircuits (various electronic circuits such as ICs, microcomputers, orcapacitors) are mounted on a top surface of the control antennasubstrate 1. The triplet line 6 includes an inner line, a shieldingground, and a shielding through hole. The receiving waveguide 5 isdisposed in plurality to form a multiple-channel configuration.Alternatively, it is also possible to have a single-channelconfiguration with a single receiving waveguide 5.

The transmitting circuit package TX includes a high-frequency circuitmounting substrate 90, which is made of a dielectric substrate such asresin or ceramic having excellent high-frequency transmissioncharacteristic. On an underside surface layer of the high-frequencycircuit mounting substrate 90 (i.e., on the surface layer of the sidefacing the control antenna substrate 1), high-frequency circuits fortransmission 91 are formed and a high-frequency semiconductor chip fortransmission 92 is mounted. As the high-frequency circuits fortransmission 91 (92), for example, there are disposed an oscillatorcircuit for generating a high-frequency signal of frequency f0, anamplifier circuit for amplifying the output of the oscillator circuit, adirectional coupler for outputting the output of the amplifier circuitto a multiplier/amplifier circuit and to the triplet line 6, and themultiplier/amplifier circuit for multiplying the output of the amplifiercircuit by N (N≧2) and outputting a multiplying signal of frequency N·f0by means of amplification. The operations of the high-frequency circuitsfor transmission 91 (92) are controlled by the control circuits mountedon the control antenna substrate 1. The high-frequency circuits fortransmission 91 (92) transmit transmitter pulses via a microstripline-waveguide converter and via the transmitting waveguide 4 and theantenna formed on the control antenna substrate 1. The transmittingwaveguide 4 is disposed in plurality to form a multiple-channelconfiguration. Alternatively, it is also possible to have asingle-channel configuration with a single transmitting waveguide 4.

The control antenna substrate 1 and the multilayer dielectric substrate90 of the transmitting circuit package TX are connected by BGA balls(solder balls) 10. DC bias and signal connection are made using the BGAballs 10. In this example, a local oscillation wave signal (LOCALsignal) of frequency f0, which is used in the high-frequency circuitsfor transmission 91 (92) of the transmitting circuit package TX, isinput to the receiving circuit package RX via the directional coupler,the BGA balls 10, the triplet line 6 of the control antenna substrate 1,and BGA balls 30.

The receiving circuit package RX includes a high-frequency circuitmounting substrate 20 (hereinafter, referred to as high-frequency resinsubstrate), which is made of a dielectric substrate of resin or ceramichaving excellent high-frequency transmission characteristic. On anunderside surface layer of the high-frequency resin substrate 20 (i.e.,on the surface layer of the side facing the control antenna substrate1), high-frequency circuits for reception 21 are formed and ahigh-frequency semiconductor chip 22 is mounted. As the high-frequencycircuits for reception 21, for example, an input-output pattern wiringthat forms portions of mixer circuits, a power divider, and an RFcircuit such as a waveguide converter can be exemplified. As thehigh-frequency semiconductor chip 22, for example, an APDP(anti-parallel diode pair) that forms portions of mixers and a chipresistor used in the power divider can be exemplified. Thehigh-frequency semiconductor chip 22 is mounted on the high-frequencyresin substrate 20 using Au bumps 100 by means of flip-chip bonding.

The BGA balls 30 are disposed as conductive connecting members on theunderside surface layer of the high-frequency resin substrate 20 thatfaces the mother control substrate 3. The BGA balls 30 perform thefollowing functions.

1) DC bias and signal connection between the high-frequencysemiconductor chip 22 and the control circuits mounted on the controlantenna substrate 1

2) Establishing connection of the local oscillation wave signal (LOCALsignal) with the triplet line 6 formed on the control antenna substrate1

3) Forming cavities for achieving operating stability of individualcircuits (mixers, power dividers, etc.)

4) Securing spatial isolation among a plurality of channels

5) Electromagnetic shielding (in place of the lid) for the receivingcircuit in entirety

6) Preventing leakage of spurious waves

Explained below with reference to FIGS. 2 to 5 are the details regardingthe receiving circuit package RX. Regarding the transmitting circuitpackage TX, since the package structure is identical to that of thehigh-frequency resin substrate 20 of the receiving circuit package RX,the detailed explanation thereof is not repeated with reference to FIGS.2 to 5. FIG. 2 is a cross-sectional view of the high-frequency resinsubstrate 20 and the mother control substrate 3. FIG. 3 is a plan viewof an arrangement example of the high-frequency circuits 21,high-frequency semiconductor chips 22, and BGA balls 30 formed on theunderside surface layer of the high-frequency resin substrate 20. FIG. 4is a cross-sectional view of a configuration of a waveguide-microstripconverter portion formed on the high-frequency resin substrate 20. FIG.5 is a perspective view of the configuration of the waveguide-microstripconverter portion formed on the high-frequency resin substrate 20. Inthe present embodiment, although the explanation is given for theexemplary case of four receiving channels, only a single channel isillustrated in FIG. 2 and only two channels are illustrated in FIG. 3.In FIG. 3, an example of a substantially half arrangement of thehigh-frequency circuits 21 and the BGA balls 30 is illustrated for twochannels. Meanwhile, the total number of channels formed on thehigh-frequency resin substrate 20 is not limited to four. That is, it isnot only possible to have two or three channels but also possible tohave five or more channels.

In FIG. 2, on the surface layer and on an inner layer of the mothercontrol substrate 3 are formed grounding conductor patterns GP (groundplanes) that are grounded in terms of high frequencies. The groundingconductor patterns GP are connected to grounding conductor vias GB(ground vias) illustrated by means of blackening. The groundingconductor vias GB are formed in the substrate lamination direction ofthe mother control substrate 3. As illustrated in FIGS. 4 and 5, thewaveguide 5 is formed by the grounding conductor vias GB arranged atpredetermined intervals (intervals equal to or smaller than ¼ of anin-dielectric-substrate effective wavelength λ of high-frequencysignals) and by the dielectric body forming the mother control substrate3. As the waveguide 5, a hollow waveguide as illustrated in FIG. 5 canbe used.

In the mother control substrate 3, the triplet line 6 is formed fortransmitting to the high-frequency resin substrate 20 the LOCAL signalthat is used in the high-frequency circuits for transmission 91 (92) ofthe transmitting circuit package TX. A signal via 40 is formed that isconnected to the triplet line 6, and a contact pad 41 is formed on thesurface layer and connected to the signal via 40. Moreover, in themother control substrate 3, a signal line 42 and a signal via 43 areformed for transmitting the output signals from the high-frequency resinsubstrate 20 (for example, intermediate frequency signals (IF signals)that are the output signals of the mixers) to the control circuitsmounted on the mother control substrate 3. Furthermore, althoughdescribed later in details, in the region on the mother controlsubstrate 3 which faces the high-frequency circuits for reception 21(including the high-frequency semiconductor chip 22) formed on theunderside surface layer of the high-frequency resin substrate 20,grounding conductor patterns GP are formed for stabilizing theoperations of the high-frequency circuits 21. The grounding conductorpatterns GP formed in the region facing the high-frequency circuits 21can be formed on the surface layer of the mother control substrate 3 or,for the purpose of achieving isolation, can be formed on the inner layerof the mother control substrate 3 in order to secure some distance fromthe high-frequency circuits 21. For electrically-shielding thehigh-frequency circuits 21, the grounding conductor patterns GP, whichare formed in the region facing the high-frequency circuits 21, formpseudo cavities together with shielding BGA balls arranged around thehigh-frequency circuits 21, grounding conductor patterns GP formed inthat region on the inner layer of the high-frequency resin substrate 20facing the high-frequency circuits 21, and grounding conductor patternsGP formed around the high-frequency circuits 21 disposed on theunderside surface layer of the high-frequency resin substrate 20 (i.e.,formed on the underside surface layer of the high-frequency resinsubstrate 20).

In FIG. 2, the BGA balls 30 are arranged in between the mother controlsubstrate 3 and the high-frequency resin substrate 20. Among them, BGAballs 30G that are connected to grounding conductors are illustratedwith hatched circles and BGA balls 30S (30S1, 30S2) that are used forsignal connection are illustrated with open circles. Among the BGA balls30G connected to grounding conductors, some are used in forming a BGAwaveguide 51 described later and some are used in forming shields orachieving isolation in order to achieve operating stability inindividual circuits. The former type of the BGA balls 30G are referredto by a reference numeral 30G1 and the latter type of the BGA balls 30are referred to by a reference numeral 30G2. Meanwhile, the BGA balls30G that are arranged around the BGA balls 30S, which are used forsignal connection, and that form a coaxial interface are referred to bya reference numeral 30G3.

In FIGS. 2 and 3, in the high-frequency resin substrate 20, awaveguide-microstrip converter (hereinafter, referred to as WG-MICconverter) 50 is formed at a position facing the waveguide 5, which isformed in the mother control substrate 3. As illustrated in detail inFIGS. 4 and 5, the WG-MIC converter 50 includes the BGA waveguide 51, awaveguide opening 52, a back-short 53, and a tip-open probe 54 formed ofa microstrip line.

The waveguide opening 52 is formed at a position facing the waveguide 5,which is formed in the mother control substrate 3, by partially notproviding the grounding conductor pattern GP formed on the undersidesurface layer of the high-frequency resin substrate 20 so that adielectric body 60 is exposed through the waveguide opening 52. Thewaveguide opening 52 is formed to surround the tip-open probe 54 formedof a microstrip line.

The BGA waveguide 51 includes the BGA balls 30G1 that are arranged atintervals equal to or smaller than ¼ of the free space propagationwavelength for high-frequency signals. In this portion, air is thesignal transmission medium. Specifically, on the underside surface layerof the high-frequency resin substrate 20, conductor lands (exposedconducting portions) 65 are formed around the waveguide opening 52 atintervals equal to or smaller than ¼ of the free space propagationwavelength for high-frequency signals in the grounding connector patternGP. On the lands 65 are arranged the BGA balls 30G1 (i.e., conductorlands function as conductor regions for BGA balls). Meanwhile, on thegrounding conductor pattern GP formed on the surface layer, aninsulating material (solder resist) is applied to the portion other thanthe lands 65.

The back-short 53 is a tip-short dielectric waveguide having the lengthof λ/4 in the lamination direction of the high-frequency resin substrate20 from the waveguide opening 52. The back-short 53 includes thegrounding conductor vias GB that are arranged at intervals smaller thanλ/8 of the in-substrate effective wavelength, and includes a dielectricbody, and includes a grounding conductor pattern GP (200) formed at thetop end. The grounding conductor pattern GP (200) is formed on a topsurface layer or on an inner layer to function as a short-circuitingplate for the dielectric waveguide. The grounding conductor pattern GP(200) is connected to the grounding conductor pattern GP formed aroundthe waveguide opening 52 and to the grounding conductor vias GB. In thesignal frequency band, the back-short 53 functions to enhance the jointcondition between the waveguide 5 and the microstrip. The tip-open probe54 is a tip-open microstrip line formed on the underside surface layerof the high-frequency resin substrate 20 in such a way that it protrudesin the waveguide opening 52. By the back-short 53, the tip-open probe 54is disposed at a position where the standing wave distribution is themaximum, so that it can perform waveguide-microstrip conversionefficiently. As described above, according to the first embodiment, thesignals from the high-frequency circuits can be input from and output tooutside using waveguides. Hence, in millimeter wave bands equal to orlarger than 60 GHz band, a high-frequency signal input-output interfaceof small size can be implemented with low loss.

Given below is an explanation regarding the high-frequency circuits forreception 21 and the high-frequency semiconductor chip 22 formed on theunderside surface layer of the high-frequency resin substrate 20. TheLOCAL signal input via the triplet line 6 and via the signal via 40 ofthe mother control substrate 3 is transmitted to the high-frequencyresin substrate 20 via the BGA ball 30S1 (illustrated in the lower rightpart in FIG. 3). Around the BGA ball 30S1 to which the LOCAL signal istransmitted, the BGA balls 30G3 are disposed in plurality (in thisexample, four) to form a coaxial interface. The BGA balls 30G3 areconnected to the grounding conductor pattern GP formed on the undersidesurface layer of the high-frequency resin substrate 20. To be precise,around the BGA ball 30S1 to which the LOCAL signal is transmitted, fourof the lands 65 are formed at which the grounding conductor pattern isexposed. On those four lands are connected the BGA balls 30G3, which arearranged at intervals equal to or smaller than ¼ of the free spacepropagation wavelength for high-frequency signals.

To the BGA ball 30S1, to which the LOCAL signal is transmitted, areconnected a conductor land 66 and a microstrip line 70 that are formedon the underside surface layer of the high-frequency resin substrate 20.To the microstrip line 70 are connected power dividers 75, and to thepower dividers 75 are connected mixers 80. In this example, since thereare four receiving channels, the power dividers 75 divide the LOCALsignal input to the microstrip line 70 into four signals. Each powerdivider 75 includes, for example, a branching circuit, an impedanceconverting circuit, a λg/2 phase line, and a chip resistor 76 as thehigh-frequency semiconductor chip 22.

In this example, since there are four receiving channels, four mixers 80are formed. Each mixer 80 includes an APDP (anti-parallel diode pair) 81as the high-frequency semiconductor chip 22, a signal line, and abranching circuit formed on the underside surface layer of thehigh-frequency resin substrate 20. In each mixer 80, the LOCAL signalinput via the power dividers 75 is mixed with an RF signal input via thetip-open probe 54, and a beat signal (IF signal) is generated thatrepresents the component of the sum of frequencies or the difference offrequencies of the LOCAL signal and the RF signal.

The IF signal output from each mixer 80 is input to the conductor lands66 for IF signals via an antiphase absorption circuit formed on theunderside surface layer or the inner layer of the high-frequency resinsubstrate 20 and via an IF signal output circuit (not illustrated) of areflective circuit. In FIG. 2, the IF signal output circuit isillustrated to be on the underside surface layer of the high-frequencyresin substrate 20. In FIG. 3, the IF signal output circuit is assumedto be on the inner layer of the high-frequency resin substrate 20, andit is not illustrated. To each land 60 for IF signals is connected oneof the BGA balls 30S2. Thus, the IF signals are transmitted to themother control substrate 3 via the BGA balls 30S2. Around the BGA balls30S2 via which the IF signals are transmitted, the BGA balls 30G3 aredisposed in plurality (in this example, six). The BGA balls 30G3 areconnected to the grounding conductor pattern GP. This portion also formsa coaxial circuit interface in an illustrated example. However, suchcoaxial circuit interface may not be formed. For example, if the IFfrequency is low, then only a single BGA ball 30G3 can be disposed sothat the signals can be transferred as parallel wire lines. Although theBGA balls 30G1 are assumed to be arranged at intervals equal to orsmaller than ¼ of the free space propagation wavelength forhigh-frequency signals, the intervals can also be widened depending onthe IF frequency band and by taking into consideration the interferenceand radioactivity. In the mother control substrate 3, the IF signals aretransmitted to the control circuits mounted on the mother controlsubstrate 3 via the signal line 42 and the signal via 43 on the surfacelayer and via the signal line 42 on the inner layer.

As described above, in the region of the mother control substrate 3,which faces the high-frequency circuits 21 (including the high-frequencysemiconductor chip 22) such as the mixers 80, the power dividers 75, andthe IF signal output circuit that are formed on the underside surfacelayer of the high-frequency resin substrate 20, the grounding conductorpatterns GP are formed for stabilizing the operations of thehigh-frequency circuits 21. Similarly, on the inner layer (first layerfrom the underside surface layer) of the high-frequency resin substrate20, the grounding conductor patterns GP are also formed in the regionfacing the high-frequency circuits 21 such as the mixers 80 and thepower dividers 75. The grounding conductor pattern GP formed on theinner layer (first layer from the underside surface layer) of thehigh-frequency resin substrate 20 is the grounding conductor for thehigh-frequency circuits 21, functions as the shielding conductor forshielding the high-frequency circuits 21 and also functions as the RTN(return) conductor of the surface layer lines (microstrip lines) of thehigh-frequency circuits 21 that are formed on the underside surfacelayer of the high-frequency resin substrate 20. The grounding conductorpattern GP formed on the inner layer (first layer from the undersidesurface layer) of the high-frequency resin substrate 20 and thegrounding conductor pattern GP formed around the high-frequency circuits21 are connected by the grounding conductor vias GB having the sameelectric potential.

Explained below with reference to FIG. 3 is an arrangement of the BGAballs. In FIG. 3, on the grounding conductor pattern GP formed on theunderside surface layer of the high-frequency resin substrate 20, thegrounding conductor lands 65 are arranged by not providing insulatingmaterial at which the grounding conductor pattern is exposed. Theintervals between the lands 65 are basically equal to or smaller than ¼of the free space propagation wavelength for high-frequency signals.Moreover, at those surface layer positions of the mother controlsubstrate 3 which face the arrangement positions of the groundingconductor lands 65 formed on the underside surface layer of thehigh-frequency resin substrate 20, identical grounding conductor landsare formed. The BGA balls 30G connect the grounding conductor landsformed on the high-frequency resin substrate 20 with the groundingconductor lands formed on the mother control substrate 3. Similarly, inorder to sandwich the BGA balls 30S that are used for DC bias and signalconnection of control signals or the LOCAL signal, lands for sandwichingare formed at the respective surface layer positions on thehigh-frequency resin substrate 20 and the mother control substrate 3.Meanwhile, in FIG. 3, the BGA balls for DC bias and for signalconnection of control signals are not illustrated.

In FIG. 3, the grounding conductor pattern GP is also formed aroundportions 55 at which the dielectric body 60 is exposed and the mixers 80are disposed. On the grounding conductor pattern GP formed around themixers 80, the lands 65, to which are connected the BGA balls 30G2 usedfor achieving shielding or isolation, are arranged surrounding themixers 80 at intervals equal to or smaller than ¼ of the free spacepropagation wavelength for high-frequency signals. The BGA balls 30G2are connected to those lands 65. The horizontal and vertical dimensionsL2 and L3 of the region surrounded by the BGA balls 30G2, which are usedfor achieving shielding or isolation, are set to be smaller than ½ ofthe free space propagation wavelength for high-frequency signals or setto avoid the length equal to ½ of the free space propagation wavelengthfor high-frequency signals. That is because, if the horizontal andvertical dimensions L2 and L3 match with substantially ½ of thewavelength corresponding to the operating frequency of thehigh-frequency circuits (i.e., match with cutoff dimensions), thenresonance occurs inside the cavities thereby causing malfunctioning(undesired oscillation, frequency fluctuation) in the high-frequencycircuits. Similarly, the BGA balls 30G2 are arranged in such a way thatthe dimension L1 is also smaller than ½ of the free space propagationwavelength for high-frequency signals. That is done because the signalsspatially propagate between the cavities housing the circuits therebycausing malfunctioning (undesired oscillation, frequency fluctuation) inthe high-frequency circuits due to feedback/joining.

As described above, in the region (on the surface layer or on the innerlayer) of the mother control substrate 3, which face the mountingregions of the high-frequency circuits such as the mixers 80, thegrounding conductor patterns GP are formed. The grounding conductorpatterns GP form pseudo shielding cavities as shielding enclosurestogether with the BGA balls 30G2 that are arranged around the mixers 80and used for achieving shielding or isolation, the grounding conductorpattern GP formed at the positions facing the mounting regions of thehigh-frequency circuits on the inner layer (first layer from theunderside surface layer) of the high-frequency resin substrate 20, andthe grounding conductor pattern GP formed on the underside surface layer(or the inner layer) of the high-frequency resin substrate 20 and aroundthe mounting regions of the high-frequency circuits. In this way, thehigh-frequency circuits are individually partitioned and are furtherpartitioned on a channel-by-channel basis by pseudo shielding cavitiesthat are formed using the BGA balls 30G2 and grounding conductorpatterns GP facing the high-frequency circuits. Thus, shielding of thehigh-frequency circuits or isolation among channels can be achievedusing a simple and inexpensive configuration and not using any lid.

In FIG. 3, the grounding conductor pattern GP is also formed around thepower dividers 75. On the grounding conductor pattern GP formed aroundthe power dividers 75, the lands 65 and the BGA balls 30G2 are alsoformed so as to surround the power dividers 75 at intervals equal to orsmaller than ¼ of the free space propagation wavelength forhigh-frequency signals. Moreover, the grounding conductor pattern GP isalso formed at those positions on the mother control substrate 3 whichface the mounting positions of the power dividers 75. Furthermore, thegrounding conductor pattern GP is also formed on the inner layer (firstlayer from the underside surface layer) of the high-frequency resinsubstrate facing the mounting regions of the power dividers 75. Becauseof such grounding conductor patterns GP, similar pseudo shieldingcavities are formed as shielding enclosures.

Moreover, in FIG. 3, in order to achieve isolation among the receivingchannels, the BGA balls 30G2 are also arranged between thehigh-frequency circuits of each receiving channel, that is, between themixers 80. Besides, in order to electromagnetically shield the circuitsin entirety, the BGA balls 30G2 are also arranged around the circuits inentirety.

Meanwhile, other than the configuration illustrated in FIG. 1, thetransmitting circuit package TX can also be configured with a multilayerdielectric substrate made of ceramic, high-frequency circuits fortransmission mounted on the multilayer dielectric substrate, and a lidfor shielding the high-frequency circuits as disclosed in JapanesePatent Application Laid-open No. 2002-185203 or in Japanese PatentApplication Laid-open No. 2004-254068. In this case, the operations ofthe high-frequency circuits for transmission are controlled by theabove-mentioned control circuits mounted on the control antennasubstrate 1. The high-frequency circuits transmit transmitter pulses viaa microstrip line-waveguide converter and via the transmitting waveguide4 and an antenna formed on the control antenna substrate 1.

Furthermore, in the receiving circuit package RX or in the transmittingcircuit package TX, as long as the size of the high-frequency resinsubstrate 20 does not cause cracks or peeling in the base material atthe joints with the mother substrate, the multilayer resin substrate canbe replaced with a multilayer ceramic substrate as the material for thehigh-frequency resin substrate 20.

Besides, if the restrictions on the BGA balls 10 are not severe from themanufacturing perspective or from the cost perspective, then the solderballs can be replaced with gold bumps and joining can be done usingpressure bonding. Moreover, if the restrictions are not severe from themanufacturing perspective, from the cost perspective, or from thereliability perspective; then the BGA balls 10 can be replaced withconductive blocks or conductive fillers for the purpose of connection.

FIG. 6 illustrates another arrangement example of the BGA balls that arearranged around the portion 55 at which the dielectric body 60 isexposed and at which the waveguide opening 52 and the mixer 80 aredisposed. In FIG. 6, the waveguide opening 52 and the exposed portion 55are spaced apart by a larger distance than the distance illustrated inFIG. 3, and two or more rows of the BGA balls are arranged in betweenthe waveguide opening 52 and the exposed portion 55 (two rows in FIG.6). Similarly to the case illustrated in FIG. 3, the BGA balls arearranged at intervals equal to or smaller than ¼ of the free spacepropagation wavelength for high-frequency signals. In this way, byarranging two or more rows of the BGA balls in between the waveguideopening 52 and the exposed portion 55, there is an enhancement in theshielding between the WG-MIC converter 50 and the mixer 80, and eachcircuit performs operations in a stable manner.

As described above, according to the present embodiment, thehigh-frequency circuits formed on the underside surface layer of thehigh-frequency resin substrate 20 are housed inside pseudo shieldingcavities that are surrounded by the BGA balls formed around thehigh-frequency circuits, surrounded by the grounding conductors disposedat the regions facing the high-frequency circuits, and surrounded by thegrounding conductors formed around the high-frequency circuits. As aresult, it becomes possible to electromagnetically shield thehigh-frequency circuits using a simple and inexpensive configuration andnot using any lid. Incidentally, the high-frequency circuits are housedin a non-airtight manner between the high-frequency resin substrate 20functioning as a first dielectric substrate and the mother controlsubstrate 3 functioning as a second dielectric substrate. Moreover, thehigh-frequency circuits that are formed on the underside surface layerof the high-frequency resin substrate 20 and that correspond to theplurality of channels are shielded by creating channel-based partitionswith pseudo shielding cavities. Hence, it becomes possible to achieveisolation among the channels using a simple and inexpensiveconfiguration and not using partitioning members such as a seal ring.

Moreover, according to the present embodiment, implementing the BGAconnection structure makes it possible to provide a high-frequencyhousing case that includes a waveguide interface (BGA waveguide 51),coaxial interfaces (BGA balls 30S1 and 30S2), and a shield/isolationstructure (pseudo shielding cavities). Therefore, it becomes possible toprovide an inexpensive sensor module having superior potential forhigh-volume production.

INDUSTRIAL APPLICABILITY

In this way, the high-frequency circuit package and the sensor moduleaccording to the present invention are suitable for mountinghigh-frequency circuits between substrates.

REFERENCE SIGNS LIST

-   -   1 CONTROL ANTENNA SUBSTRATE    -   2 RESIN ANTENNA SUBSTRATE    -   3 MOTOR CONTROL SUBSTRATE    -   4 TRANSMITTING WAVEGUIDE    -   5 RECEIVING WAVEGUIDE    -   6 TRIPLET LINE    -   10 BGA BALL    -   20 HIGH-FREQUENCY CIRCUIT MOUNTING SUBSTRATE (HIGH-FREQUENCY        RESIN SUBSTRATE)    -   21 HIGH-FREQUENCY CIRCUIT    -   22 HIGH-FREQUENCY SEMICONDUCTOR CHIP    -   30 BGA BALL    -   30G, 30G1, 30G2, 30G3 BGA BALL (GROUND CONNECTION)    -   30S, 30S1, 30S2 BGA BALL (FOR SIGNAL)    -   40, 43 SIGNAL VIA    -   41 CONTACT PARD    -   42 SIGNAL LINE    -   50 WAVEGUIDE-MICROSTRIP CONVERTER    -   51 BGA WAVEGUIDE    -   52 WAVEGUIDE OPENING    -   53 BACK-SHORT    -   54 TIP-OPEN PROBE    -   55 PORTION OF EXPOSED DIELECTRIC BODY    -   60 DIELECTRIC BODY    -   65 CONDUCTOR LANDS (GROUND CONNECTION)    -   66 CONDUCTOR LANDS (SIGNAL CONNECTION)    -   70 MICROSTRIP LINE    -   75 POWER DIVIDER    -   76 CHIP RESISTOR    -   80 MIXER    -   81 APDP    -   90 HIGH-FREQUENCY CIRCUIT MOUNTING SUBSTRATE    -   91 HIGH-FREQUENCY CIRCUIT FOR TRANSMISSION    -   92 HIGH-FREQUENCY SEMICONDUCTOR CHIP FOR TRANSMISSION    -   100 Au BUMP    -   GB GROUNDING CONDUCTOR VIA    -   GP GROUNDING CONDUCTOR PATTERN    -   RX RECEIVING CIRCUIT PACKAGE    -   TX TRANSMITTING CIRCUIT PACKAGE

The invention claimed is:
 1. A high-frequency circuit packagecomprising: a first dielectric substrate having a high-frequency circuitformed and disposed on an underside surface layer and having a firstgrounding conductor that has a same electric potential as a groundingconductor of the high-frequency circuit and that is formed on theunderside surface layer to surround the high-frequency circuit; a seconddielectric substrate, on which the first dielectric substrate is mountedin such a way that the high-frequency circuit is sandwichedtherebetween, the second dielectric substrate having a second groundingconductor formed in a region that faces the high-frequency circuit; andsolder balls for connecting a plurality of conductor lands andsurrounding the high-frequency circuit at positions at which the firstand second grounding conductors face each other, the conductor landsbeing arranged at intervals smaller than ¼ of an operating signalwavelength for the high-frequency circuit, wherein the high-frequencycircuit is housed in a pseudo shielding cavity that is formed due tomutual connection established between the first and second dielectricsubstrates by the solder balls, and that includes the plurality ofsolder balls, the first and second grounding conductors, and thegrounding conductor of the high-frequency circuit, the first dielectricsubstrate includes a microstrip line that is connected to thehigh-frequency circuit and that is formed on the underside surfacelayer; a waveguide opening formed by partially not providing the firstgrounding conductor so as to surround a tip-open portion of themicrostrip line; and a tip-short dielectric waveguide that iselectrically connected to the waveguide opening and that has the lengthof substantially ¼ of an in-substrate effective propagation wavelengthfor high-frequency signals in a substrate lamination direction from thewaveguide opening; the second dielectric substrate includes a waveguidethat is formed at a position facing the waveguide opening and that isformed in a substrate lamination direction, and a plurality of waveguideconductor lands, which are arranged at positions of the first and secondgrounding conductors facing each other at intervals equal to or smallerthan ¼ of a free space propagation wavelength for high-frequency signalsso as to surround the waveguide opening and the waveguide, are mutuallyconnected by solder balls to take out an input-output signal of thehigh-frequency circuit through the waveguide of the second dielectricsubstrate.
 2. The high-frequency circuit package according to claim 1,wherein the first dielectric substrate includes, on the undersidesurface layer, a first wiring pattern that is connected to thehigh-frequency circuit and that transmits a DC bias and a control signalfor driving the high-frequency circuit; and first signal lands connectedto the wiring pattern; the second dielectric substrate includes a DCpower source and a control circuit mounted thereon for driving thehigh-frequency circuit; the second dielectric substrate includes, on amounting surface for the first dielectric substrate, a second wiringpattern for transmitting signals from the DC power source and thecontrol circuit; and a plurality of second signal lands that areconnected to the second wiring pattern and that are formed at positionsfacing the first signal lands; and the first and second signal landsfacing each other are mutually connected by solder balls so that the DCpower source and the control circuit mounted on the second dielectricsubstrate drive the high-frequency circuit mounted on the firstdielectric substrate.
 3. The high-frequency circuit package according toclaim 1, wherein the second grounding conductor formed on the seconddielectric substrate is electrically connected to the plurality ofconductor lands that surround the high-frequency circuit at intervalssmaller than ¼ of an operating signal for the high-frequency circuit andis formed on the surface layer or the inner layer of the seconddielectric substrate.
 4. The high-frequency circuit package according toclaim 1, wherein horizontal and vertical dimensions of a region, whichis surrounded by the solder balls for connecting the plurality ofconductor lands that are formed to surround the high-frequency circuitat positions at which the first grounding conductor and the secondgrounding conductor face each other and that are arranged atpredetermined intervals smaller than ¼ of an operating signal wavelengthfor the high-frequency circuit, are set to be smaller than ½ of a freespace propagation wavelength for high-frequency signals or set to avoidthe length equal to ½ thereof.
 5. The high-frequency circuit packageaccording to claim 1, wherein a plurality of the high-frequency circuitsare formed and disposed on the underside surface layer of the firstdielectric substrate, the first dielectric substrate includes aplurality of the microstrip lines respectively connected to theplurality of high-frequency circuits, a plurality of the waveguideopenings, and a plurality of the tip-short waveguides, the seconddielectric substrate includes a plurality of the waveguides formed atpositions facing the plurality of waveguide openings and formed in asubstrate lamination direction, and the plurality of waveguide conductorlands, which are arranged on the first grounding conductor and on thesecond grounding conductor at positions facing each other at intervalsequal to or smaller than ¼ of a free space propagation wavelength forhigh-frequency signals to surround the plurality of waveguide openingsand the plurality of waveguides, are mutually connected by the solderballs to take out an input-output signal of each of the high-frequencycircuits through the waveguides of the second dielectric substrate. 6.The high-frequency circuit package according to claim 1, wherein thehigh-frequency circuit is housed in a non-airtight manner in between thefirst dielectric substrate and the second dielectric substrate.
 7. Asensor module comprising: the high-frequency circuit package accordingto claim 1; and an antenna that is disposed on the second dielectricsubstrate on the opposite side of the mounting surface for the firstdielectric substrate and that is connected to the waveguide.
 8. Ahigh-frequency circuit package for housing a high-frequency circuit,comprising: a high-frequency circuit mounting substrate as a firstdielectric substrate that includes a microstrip line that is connectedto the high-frequency circuit formed on an underside surface layer andthat is formed on the underside surface layer; a waveguide opening thatis formed to surround a tip-open portion of the microstrip line and thatis formed by not providing a first grounding conductor formed on theunderside surface layer; a tip-short dielectric waveguide having alength of substantially ¼ of an in-substrate effective propagationwavelength for high-frequency signals in a substrate laminationdirection from the waveguide opening; a first solder-ball-mountingconductor land group arranged on the first grounding conductor, so as tosurround the waveguide opening, at intervals equal to or smaller than ¼of a free space propagation wavelength for high-frequency signals; asecond grounding conductor disposed around the high-frequency circuit; athird grounding conductor that functions as a return conductor for thehigh-frequency circuit and for the microstrip line, and that is formedon a substrate inner layer; a second solder-ball-mounting conductor landgroup arranged on the second grounding conductor, so as to surround thehigh-frequency circuit, at intervals equal to or smaller than ¼ of afree space propagation wavelength for high-frequency signals; and athird solder-ball-mounting conductor land group that functions totransmit a DC bias and a control signal for driving the high-frequencycircuit; a mother control substrate as a second dielectric substrate, onwhich the high-frequency circuit mounting substrate is mounted in such away that the high-frequency circuit is sandwiched therebetween, themother control substrate including a fourth grounding conductor formedin a region that faces the high-frequency circuit mounted on thehigh-frequency circuit mounting substrate; a plurality of fourthconductor land groups that are electrically connected to the fourthgrounding conductor and that are formed at positions facing the first,second, and third solder-ball-mounting conductor land groups; awaveguide formed at a position facing the waveguide opening of thehigh-frequency circuit mounting substrate and formed in a substratelamination direction; and a line that transmits a DC bias and a controlsignal for driving the high-frequency circuit; and a solder ball groupfor connecting the first to third solder-ball-mounting conductor landgroups with the plurality of fourth conductor land groups, wherein thehigh-frequency circuit is housed in a pseudo shielding cavity formed bythe solder balls connected to the second solder-ball-mounting conductorland group and by the second to fourth grounding conductors.
 9. Thehigh-frequency circuit package according to claim 8, wherein thehigh-frequency circuit mounting substrate includes, on the undersidesurface layer, a first wiring pattern that is connected to thehigh-frequency circuit and to the third solder-ball-mounting conductorland group, and that transmits a DC bias and a control signal fordriving the high-frequency circuit, the mother control substrateincludes a DC power source and a control circuit mounted thereon fordriving the high-frequency circuit; the mother control substrateincludes, on a mounting surface for the high-frequency circuit mountingsubstrate, the line that is connected to the DC power source and thecontrol circuit for transmitting the DC bias and the control signal; andfifth conductor lands that are connected to the line and included in theplurality of fourth conductor land groups, and that are formed atpositions facing the third solder-ball-mounting conductor land group;and the third solder-ball-mounting conductor land group and the fifthconductor lands facing each other are mutually connected by the solderballs so that the DC power source and the control circuit mounted on themother control substrate drive the high-frequency circuit mounted on thehigh-frequency circuit mounting substrate.